1. Field of the Invention
This invention concerns methods and hydrocyclone apparatus which are employed to separate two types of solid particles from an aqueous slurry containing both types of particles. More particularly the present invention concerns a hydrocyclone having a dual feed inlet for aqueous slurry.
2. Description of the Prior Art
Hydrocyclones are employed to separate heavy particles from lighter particles and to separate large particles from smaller particles. The heavy/large particles have greater mass than the light/small particles. Hydrocyclones are of particular value in the coal cleaning industry where the ash-rich particles of raw coal (relatively heavy--i.e., higher density) are separated from the low ash particles (relatively light--i.e., lower density).
The hydrocyclone employs the fluid pressure of the slurry to create rotational movement within a cylindrical chamber. The outlets, top and bottom, are centrally located whereby the liquid moves in a spiral path to leave the hydrocyclones. One type of suspended solid particle (heavy/large) moves outwardly and downwardly while the other type of suspended solid particle (light/small) moves radially inwardly. The rotation of aqueous slurry within the hydrocyclone is initiated by the tangential injection of the slurry into the hydrocyclone. While hydrocyclones are normally positioned with the inlet/outlet axis vertical, other dispositions are known and are effective since the gravitational forces are relatively insignificant in the operation of the hydrocyclone.
Hydrocyclones having two feed inlet openings are described in U.S. Pat. No. 4,090,956 wherein two separate feed inlets are provided diametrically opposed to each other across a cylindrical section of a hydrocyclone. One of the described objectives of the dual feed inlet hydrocyclone is to provide more uniform wear of the inner wall of the apex cone of the hydrocyclone.
The dual feed inlet hydrocyclone of the prior art, having the separate feed conduits, presents serious installation, operating and maintenance problems.
Hydrocyclones are known wherein the aqueous slurry feed inlet stream is introduced through a single feed conduit which is tangential to the cylindrical surface of the cylindrical portion of the hydrocyclone along (a) the center line of the feed conduit; (b) the adjacent surface of the feed conduit; (c) the remote surface of the feed conduit; or (d) some other line between the surfaces of the feed conduit. See "The Hydrocyclone," D. Bradley, Pergamon Press, 1965, page 119.